Market available consumer batteries such as button cell batteries or zinc-carbon batteries are generally called primary cells. These batteries are designed to be used once and then discarded. However, the heavy metals and electrolytes contained in primary cells are harmful to the environment and can result in environmental pollution when the primary cells are discarded. For example, if electrolytes contained in the primary cells leak out, this may cause a chemical reaction with water, which will then produce toxic substances.
In recent years, there has been significant progress in the research on alternatives to traditional primary cells. A water-activated power generating device, generally known as a water battery, is an example of the alternatives. Unlike traditional primary cells, a water battery is made of materials that are environmentally friendly, which means that when a water battery is discarded, the materials contained in the water battery can be easily recycled and do not produce toxic substances.
However, existing water batteries have some disadvantages. A traditional water battery often has a container for holding water, and the container needs to be carefully sealed to prevent the water in the container from leaking out. The water in the container reduces the portability of existing water batteries because a user usually has to be more careful when carrying a container filled with water together with his/her valuable belongings.
Another disadvantage is that the wastes produced during chemical reactions are usually deposited within the container of the water battery, and the wastes will affect the efficiency of chemical reactions and thus reduce the overall life span of the water battery. Furthermore, the wastes are usually difficult to clean up. Therefore, there is a need to develop a water-activated power generating device that overcomes the above-mentioned advantages.